1. Field of the Invention
The present invention relates to a method for treating a substrate with a temporary fixing material, to a composition which can form a temporary fixing material suited for temporarily fixing a substrate onto a support during processing of the substrate, and to a semiconductor device.
2. Description of the Related Art
Substrates such as semiconductor wafers need to be temporarily fixed to supports via materials such as temporary fixing materials to make sure that the substrates will not move and become displaced with respect to the supports during processing or transportation. The substrates are separated from the supports after the completion of processing and/or transportation. Several types of adhesives proposed in the art are possibly applicable to the temporary fixation of substrates (see, for example, Patent Literature 1).
Patent Literature 1 describes a wafer bonding and separating method including providing a stack including a first substrate and a second substrate bonded together via a bonding layer; subjecting the stack to a temperature of at least about 190° C. so as to soften the bonding layer; and applying a force to at least one of the first substrate and the second substrate so as to separate the first substrate and the second substrate.
In recent technologies such as photofabrication, substrates are often exposed to a high temperature environment. For example, in a mounting step in the manufacturing of stacked chips, wafers or chips are temporarily fixed to supports, then the wafers or chips are processed (for example, subjected to throughhole formation, bump formation, rewiring, wafer thinning and wafer dicing) and the chips are stacked (for example, a plated metal is melt flowed to form an electrical connection between chips), and the chips are separated from the supports.
In such a case, a temporary fixing material is desirable which allows a substrate to be separated from a support while preventing, for example, wearing or collapse of bumps on the substrate. The bonding method described in Patent Literature 1 achieves a good yield when the substrate to be processed has heat resistant bumps (for example, copper bumps). When the substrate having poorly heat resistant bumps (for example, a bump consisting of a copper portion and a solder portion) is processed, however, the solder portion is softened by a heat treatment at high temperature for separating the substrate, and the bumps are damaged.    Patent Literature 1: JP-A-2010-506406